Airplanes capable of supersonic flight, i.e., at speeds equal or greater than a Mach number of 1.0, typically use one or more engines mounted on each side of the airplane. Such airplanes can experience a large yawing moment in the unlikely event that one or more engines on one side of the airplane malfunctions or fails. That undesirable yawing moment may be caused by thrust loss from the failing or failed engine when it is opposed by an operating engine(s) on the other side of the airplane and by the pressures generated by a bow shock formed proximate the failed engine.
For safe flight to continue, flight controls are designed to counter this yawing moment. Such controls typically comprise vertical tails, rudders, and/or spoiler slot deflectors on the wing.
Conventional vertical tails and rudders produce yawing moments by deflecting the rudder surface to generate a side force. Since the generated side force occurs aft of the center of gravity (normally positioned proximate the landing gear), a yawing moment is created. As is well understood in the art, the aircraft designer has long been plagued with the problem of loss of aerodynamic control effectiveness due to structural flexibility. This means that the cantilevered structures, i.e., the vertical tail and rudder, twist under load. As a result of such elastic losses, and depending upon the structural design, such structures may lose nearly three quarters of their effectiveness. Thus, the yawing moment that a vertical tail or rudder can theoretically produce is reduced by three quarters (75%). The cantilever structure supporting the vertical tail assembly may also be cantilevered from the aft pressure bulkhead of the fuselage resulting in a very inefficient structure.
Conventional spoiler slot deflectors generate yawing moments by generating drag and changing the pressures over the wing of the airplane. A spoiler on the top or bottom of the wing and a deflector on the bottom or top of the wing defines an opening through the wing. Spoiler slot deflectors are very effective because they do not experience large elastic losses. On the other hand, these deflectors require a large hole in the wing structure thereby undesirably impacting outboard wing support, trailing edge flap supports and trailing edge flap actuation. Indirectly a spoiler slot deflector adds weight, reduces the effectiveness of outboard wing controls and the overall performance of the wing and airplane.
Flight control surfaces capable of producing various types of aerodynamic forces and moments are well known. For example, see the flaps of Browning, U.S. Pat. No. 2,496,083, issued Jan. 31, 1940; the fuselage flaps of Geary, U.S. Pat. No. 3,848,831, issued Nov. 19, 1974; the canards of Caldwell, et al., U.S. Pat. No. 4,542,866, issued Sep. 24, 1985; the control panels of Pinson, U.S. Pat. No. 4,624,424; the deflecting strakes of Rao, et al, U.S. Pat. No. 4,786,009, issued Nov. 22, 1988, the yaw producing rotatable strakes of U.S. Pat. No. 4,917,333; and the forebody flow controller of Moskovitz, U.S. Pat. No. 5,050,819, issued Sep. 24, 1991.
However, the body spoiler of the present invention can more effectively produce a high percentage of the necessary yawing moment without some of the negative aspects of the typical flight controls mentioned above. In doing so, it can reduce the size and weight of conventional flight controls such as vertical tails, rudders, and/or spoiler slot deflectors on the wing.